1. Field of Invention
The present invention relates to an electromagnetic relay in a type of xe2x80x9cslim type relayxe2x80x9d.
2. Related Art
FIG. 1 is a perspective view showing an electromagnet used in a conventional electromagnetic relay. In the electromagnet fixing structure shown in this figure, a yoke 1011, shaped like L, includes a bent surface portion 111. A rectangular through hole 112 is formed in the bent surface portion 111. A rod-like iron core 1082 is configured such hat one end of the iron core is somewhat smaller in cross section than the rectangular through hole 1112, and the other end is provided with a flange 1122. One end of the iron core 1082 is inserted into the through hole 1112, thereby fixing the yoke 1011 and the iron core 1082. The yoke 1011 and the iron core 1082 in the an electromagnet fixing structure are used together with a coil block 1013 which includes a cylindrical bobbin 1131 on which a coil 1132 is wound and a pair of coil terminals 1133 electrically connected to the coil 1132, whereby an electromagnet is formed.
FIG. 2 is an exploded perspective view showing another conventional electromagnet, and FIG. 3 is a perspective view showing the electromagnet shown in FIG. 2. In the electromagnet fixing structure shown in FIG. 2, a piece 1091, shaped like L, includes a bent surface portion 1111. A rectangular through hole 1912 is formed in the bent surface portion 1911. An iron core 1092 is shaped like L: one end of the iron core is somewhat larger in cross section than the through hole 1912 and the other end is bent. One end of the iron core 1092 is inserted into the through hole 1912, thereby fixing the yoke 1091 and the iron core 1092. The yoke 1091 and the iron core 1092 in the an electromagnet fixing structure, as shown in FIGS. 2 and 3, are used together with a coil block 1023 which includes a cylindrical bobbin 1231 on which a coil 1232 is wound and a pair of coil terminals 1233 electrically connected to the coil 1232, whereby an electromagnet is formed.
A metal member fixing method which can fix a metal member without generating metallic powder by plastically deforming a metal member with a press-fitting punch having a spherical end is disclosed JP-A-9-314255.
In a thin-type electromagnetic relay which is high in electrical insulation and small in mounting area, an armature is generally separated from a contact block in order to secure a high electrical insulation. As a result, a card to drive a contact spring by the armature is long, and a weight of a movable portion is increased. Since its structure is designed to be thin, the coil block is also thin, so that a magnetic efficiency of the resultant electromagnetic relay is lower than that of the electromagnetic relay using a circular electromagnet.
To solve such a problem, it is necessary to improve a contact opening/closing ability as possible by increasing a contact pressure since a contact chamber is designed with an intention of space saving. To this end, it is necessary to increase an attraction force by the electromagnet. To increase the attraction force, it is desirable to reduce a magnetic resistance in a coupling portion of the iron core with the yoke where the largest magnetic loss occurs. For this reason, a called spin press-fitting is conventionally employed.
In the an electromagnet fixing structure for the yoke and the iron core shown in FIGS. 1 to 3, as seen from a cross sectional view shown in FIG. 4, it is difficult to manage the protruded portions (portion A in FIG. 4A) of the iron core protruded from the surface of the yoke. That is, the protruded portions of the iron cores from the yoke surfaces are not uniform in dimension. If the protruded portions of the iron cores vary in dimension, as shown in FIG. 1, the portions on both sides of the through hole in the bent surface (both sides in FIG. 1) are expanded to be deformed when the spin press-fitting is carried out. As a result, sometimes a gap is created (left) between the yoke and the iron core.
Further, in this structure, sometimes the iron core is tilted at the time of spin press-fitting, so that the exact positioning is not exact. In this case, the magnetic coupling is weakened, so that the attraction force by the electromagnet is reduced in magnitude.
FIGS. 5 through 7 show another example of a conventional electromagnetic relay. The electromagnetic relay is made up of 1) an electromagnetic block which includes an electromagnet 1201 formed such that a coil 1204 is wound on a coil bobbin 1203 with an iron core 1202 inserted into the central part of the coil bobbin, a yoke 1205xe2x80x2, shaped like U, integrally formed with an upright portion 1205axe2x80x2 magnetically coupled to a first magnetic pole 1201a of the electromagnet 1201 and a lateral portion 1205b+ extending from an end of the upright portion 1205axe2x80x2 to a position near a second magnetic pole 1201b of the electromagnet 1201, 2) an armature 1206 which is disposed facing the second magnetic pole 1201b of the electromagnet 1201 and rotatable about the end of the yoke 1205xe2x80x2, and 3) a hinge spring 1208 for rotatably supporting the armature 1206 which the hinge spring is fixed at one end to the lateral portion 1205bxe2x80x2, of the yoke 1205xe2x80x2 and at the other end to the armature 1206, a card 1207 which is fixed to the free end of the armature 1206 and translates with the turning of the armature 1206, 4) a pair of fixed contact plates 1209 and 1210 which are fastened at first ends to fixed contacts 1209a and 1210a which are oppositely disposed, 5) a movable contact plate 1211 with movable contacts 1211a fastened on both sides of one end thereof, which the movable contact plate is turned with the translation of the card 1207, the movable contacts 11a being brought into contact with and separated from the fixed contacts 1209a and 1210a, 6) a base 1215, made of insulating synthetic resin, including fixed contact plates 1209 and 1210 and the movable contact plate 211 being provided at a first end of the base 1215, and the electromagnetic block being provided on the other end, 7) external terminals 1212 which are electrically connected to the fixed contact plates 1209 and 1210 and the movable contact plate 1211, while protruding from the underside of the base 1215, 8) a terminal support 1213, made of synthetic resin, for supporting coil terminals 1214 connected to the coil 1204 located under the armature 1206, and 9) a case 1216, shaped like a box, which is attached to the electromagnetic block and the base 1215 in a state that the external terminal 1212 and the coil terminals 1214 are projected to exterior.
An operation of the thus constructed electromagnetic relay will be described. In a stationary sate in which no voltage is applied to between the coil terminals 1214, no attraction force by the electromagnet 1201 is present. In this state, the armature 1206 is held at a position (referred to as xe2x80x9cstationary positionxe2x80x9d) located apart from the second magnetic pole 1201b of the electromagnet 1201. The movable contact plate 1211 is disposed on the base 1215 so as to press the movable contacts 1211a against the fixed contact 1209a, which is located close to the electromagnetic block (the normally closed side). Accordingly, when the armature 1206 is at the stationary position, the card 1207 has been moved to the left in FIG. 5. And the movable contact plate 1211 is not pressed by the end of the card 1207. Therefore, the movable contacts 1211a is held in a state that the movable contacts 1211a is in contact with the fixed contact 1209a on the normally closed side (this state will be (referred to as xe2x80x9cstationary statexe2x80x9d). Incidentally, a contact pressure between the movable contacts 1211a and the fixed contact 1209a is produced by a spring force of the movable contact plate 1211 made of elastic material.
When in a stationary state, a predetermined voltage (higher than a responsive voltage) is applied to between the coil terminals 1214, the armature 1206 that is attracted to the second magnetic pole 1201b of the electromagnet 1201 is turned about the end of the yoke 1205xe2x80x2, while resisting the hinge spring 1208 and a spring force of the movable contact plate 1211, and is attracted to the second magnetic pole 1201b. In turn, the card 1207 is translated to the right in FIG. 5 by the turning of the armature 1206. The end of the card 1207 pushes the movable contact plate 1211 to turn in the right direction in FIG. 5. The movable contacts 1211a fastened to the movable contact plate 1211 moves apart from the fixed contact 1209a on the normally closed side and comes in contact with the fixed contact 1210a. As a result, the movable contact is switched to another fixed contact. When the voltage applied to between the terminals 1214 drops to below a release voltage, the armature 1206 that is released from the attraction by the electromagnet 1201 is returned to the stationary position with the aid with the spring forces of the hinge spring 1208 and the movable contact plate 1211. Since the pressure by the card 1207 is removed, the movable contact plate 1211 is returned to the stationary state, and the movable contact 1211a moves apart from the fixed contact 1210a and comes in contact with the fixed contact 1209a on the normally closed side. In this way, the movable contact is switched to another fixed contact.
When the electromagnetic relay is operating, the iron core 1202 and the yoke 1205xe2x80x2 form a closed magnetic circuit. A contact area between the hinge spring 208 and the yoke 1205xe2x80x2 at the end of the lateral portion 1205bxe2x80x2 of the yoke 1205xe2x80x2 serving as a fulcrum when the armature 1206 is turned, is small. Therefore, a magnetic resistance in this area is large, so that an attraction force of the electromagnet 1201 exerting armature 1206 reduces in magnitude.
Another conventional electromagnetic relay as shown in FIGS. 8 and 9 is known as this type of the electromagnetic relay. As shown, the electromagnetic relay is made up of electromagnetic block 1301 with an armature 1316, a card 1302, a contact portion 1303, a body 1304, and a cover 1305. The armature 316 of the electromagnetic block 1301 is reciprocatively driven when current is fed to a coil thereof.
The card 1302 is driven through the reciprocal motion of the armature 1316 to open and close a contact portion 1303 to be described later. The contact portion 1303 includes a normally closed contact plate 1330, made of conductive material, having a normally open contact 1330a at an end thereof, a normally open contact plate 1332, made of conductive material, having a normally open contact 1332a at an end thereof, and a movable contact plate 1331, made of conductive material, having movable contacts 1331a on both sides of one end thereof, which the contacts 1331a may be brought into contact with and separated from the normally open contact 1330a and the normally open contact 1332a. The body 1304, made of synthetic resin, includes contact plates 1330 to 1332 are located at one end when viewed in the longitudinal direction and accommodating grooves 1349a to 1349c located at the same end and opened to one side when viewed in the width direction. The body 1304 further includes an accommodating concavity portion 1342 for receiving the electromagnetic block 1301, which is located at the other end when viewed in the longitudinal direction and opened to the other side when viewed in the width direction. The cover 1305, shaped like a box, is made of synthetic resin, and opened at one side. The body 1304 is set covering the electromagnetic block 1301, the contact portion 1303 and the like.
The electromagnetic block 1301 is placed in the accommodating concavity portion 1342 with the armature 1316 being located in opposition to the contact portion 1303. The card 1302, shaped like a plate, includes engaging pawls 1321 at one end. The engaging pawls 1321 are brought into engagement with depressed parts 1316a, which are formed in both side edges of the extreme end of the armature 1316. The card 1302 further includes a pressing member 1322 at the other end. The pressing member 1322 is used for pressing the movable contact plate 1331. A protruded piece 1323 is provided at the extreme end of the pressing member 1322, and is to be inserted into a hole 1331c bored in an end of the movable contact plate 1331. The engaging pawls 1321 of the card 1302 are respectively brought into engagement with the depressed parts 1316a. The protruded piece 1323 of the pressing member 1322 is inserted into the hole 1331c of the movable contact plate 1331. The card 1302 is bridged between the armature 1316 and the movable contact plate 1331 while being confronted with a wall 1341 forming the ceiling of the accommodating concavity portion 1342. The width of the pressing member 1322 of the card 1302 is shorter than the width of the remaining portion thereof. The pressing member 1322 of the card 1302 is disposed closer to the side of the accommodating concavity portion 1342, which is opposite to the closed side thereof. Accordingly, there is no chance that the pressing member 1322 interferes with ribs 1305a and 1305b, which are protruded from the inner surface of the cover 1305. Those ribs will be described later.
In the electromagnetic relay, the contact plate 1330 to 1332 are disposed on one side of the body 1304 when viewed in the width direction, and the electromagnetic block 1301 is disposed on the other side. With this structure, a long insulation distance is secured between the contact portion 1303 and the electromagnetic block 1301, to thereby improve the insulating performance of the electromagnetic relay. Grooves 1344 and 1345 are formed in an insulation wall 1343, which separates the accommodating concavity portion 1342 from a space closer to the contact portion 1303. The grooves 1344 and 1345 extend along the opening edge of the accommodating concavity portion 1342. A couple of ribs 1305a and 1305b for receiving the grooves 1344 and 1345 are protruded from the inner surface of the cover 1305. Therefore, when the cover 305 is applied to the body 1304, the ribs 1305a and 1305b of the cover 1305 are inserted into the grooves 1344 and 1345, respectively, so that those ribs 1305a and 1305b insulate the electromagnetic block 1301 from the contact portion 1303.
When the electromagnetic relay is reduced in size, the shortest distance (indicated by xe2x80x9caxe2x80x9d in FIG. 8B) is reduced which is measured along the surface of the wall 1341 located between the electromagnetic block 1301 and the contact portion 1303, and the surface of the card 1302. Therefore, there is a chance of failing to secure an insulation distance (creeping distance), which is required for providing a desired electrical insulation performance.
When the cover 1305 is attached to the body 1304, a height position of the cover 1305 with respect to the body 1304 is approximately determined when the lower ends of the ribs 1305a and 1305b protruded from the inner surface of the cover 1305 are brought into contact with the bottoms of the grooves 1344 and 1345. In this case, the positioning of them is not precise, however. For this reason, the height positions of the cover 1305 to the body 1304 are not uniform among the products of the electromagnetic relays.
Accordingly, an object of the present invention is to provide an electromagnet fixing structure of an electromagnetic relay which can increase an attraction force by an electromagnet, and a method of fixing the electromagnet.
Accordingly, another object of the present invention is to provide an electromagnetic relay which increases an attraction force of an electromagnet exerting on the armature without increase of cost, and a method of manufacturing an electromagnetic relay which is easy in managing the thick dimensions when the yokes are manufactured.
Accordingly, another object of the present invention is to provide an electromagnetic relay of which the insulation performance is improved. Another object of the present invention is to provide an electromagnetic relay in which the cover can precisely be positioned to the body.
According to an aspect of the present invention, there is provided an electromagnetic relay comprising:
a rectangular iron core with a coil wound thereon;
a plate-like yoke of which one end is magnetically coupled with one magnetic pole of said iron core and the other end is extended to a position near the other magnetic pole of said iron core, said other end of said yoke having an enlarge contact area increase surface shaped like L;
an armature rotatably and pivotally supported by said other end of said yoke;
a movable contact movable with a movement of said armature; and
a fixed contact brought into contact with and separated from said movable contact.
According to another aspect of the present invention, there is provided a method of forming an electromagnetic relay including:
a rectangular iron core with a coil wound thereon;
a plate-like yoke of which one end is magnetically coupled with one magnetic pole of said electromagnet and the other end is extended to a position near the other magnetic pole of said electromagnet, said other end of said yoke having an enlarge contact area increase shaped like L;
an armature rotatably and pivotally supported by said other end of said yoke, said armature being driven by said coil; a movable contact being movable with a turn of said armature; and
a fixed contact being brought into contact with and separated from said movable contact, said method comprising the steps of:
bending said other end of said yoke to have a shape like L; and
shaving-machining said L-shaped portion to form a fulcrum of said armature when said armature is turned.
According another aspect of the present invention, there is provided an electromagnetic relay including:
a rectangular iron core with a coil wound thereon;
a plate-like yoke of which one end is magnetically coupled with one magnetic pole of said iron core and the other end is extended to a position near the other magnetic pole of said iron core, said other end of said yoke having an enlarge contact area increase surface shaped like L;
an armature rotatably and pivotally supported by said other end of said yoke, said armature being driven by said coil;
a movable contact being movable with a turn of said armature; and
a fixed contact being brought into contact with and separated from said movable contact, said electric magnet prepared by the process comprising the steps of:
bending said other end of said yoke to have a shape like L; and
shaving-machining said L-shaped portion to form a fulcrum of said armature when said armature is turned.
According to another aspect of the present invention, there is provided an electromagnet comprising:
a plate-like yoke, shaped like L, with a curved surface portion;
a rectangular iron core connected to said yoke and wound by a coil;
an armature rotatably and pivotally supported by one end of said yoke, said armature being driven by said coil; and coupling means for coupling said yoke with said iron core by spin press-fitting.
According to another aspect of the present invention, there is provided an electromagnet comprising:
a plate-like yoke, shaped like L, with a curved surface portion;
a rectangular iron core connected to said yoke and wound by a coil;
an armature rotatably and pivotally supported by one end of said yoke, said armature being driven by said coil; and
coupling means for coupling said yoke with said iron core by spin press-fitting.
According to another aspect of the present invention, there is provided an electromagnet comprising:
an electromagnet assembly including:
a rectangular iron core with a coil wound thereon;
a plate-like yoke of which one end is magnetically coupled with one magnetic pole of said electromagnet and the other end is extended to a position near the other magnetic pole of said electromagnet, said other end of said yoke having an enlarge contact area increase shaped like L; and
an armature rotatably and pivotally supported by said other end of said yoke;
a contact assembly including;
a movable contact movable through a movement of said armature;
a fixed contact brought into contact with and separated from said movable contact; and
coupling means for coupling said yoke with said iron core by spin press-fitting.
According to another aspect of the present invention, there is provided an electromagnet further comprising:
a card for moving said movable contact through a movement of said armature; and
a main body including contact plates at one end and an accommodating concavity portion opened sideways at the other end, said assembly being placed in said accommodating concavity portion, said main body including a ceiling wall with a protrusion.
According to another aspect of the present invention, there is provided an electromagnet relay, further comprising:
a box-like cover one of which is opened, said cover being attached to said main body while covering said electromagnet block, said contact portion, and said card; and
a positioning member for keeping a distance between said ceiling wall of said main body and a wall of said cover at a fixed distance.